c. 1300, "matching, similar, corresponding" (a sense now obsolete), present-participle adjective and adverb from accord (v.). Meanings "conforming (to), compliant, in agreement; consistent, harmonious; suitable, appropriate" are from late 14c. According to "referring to," literally "in a manner agreeing with" is from late 14c. As an adverb, "often applied to persons, but referring elliptically to their statements or opinions" [Century Dictionary].
late 14c., "done in consequence of or in prosecution of something," from Anglo-French pursuant, from Old French poursuiant, porsivant, present participle of porsuir, porsivre "chase, pursue" (see pursue). Meaning "carrying out; following, according" is from 1690s. As an adverb, "according, agreeably," 1670s. As a noun, "one who seeks, an aspirant," late 14c.